GMC 1996 Sierra Owner's Manual page 41

I
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You can be seriously hurt if your shoulder belt is
too loose. In a crash, you would move forward
too much, which could increase injury. The
shoulder belt should fit against your body.
To unlatch the belt, just push the button on the buckle.
Rear Seat Outside Passenger Positions
(Crew Cab)
If you have an Extended Cab, see "Rear Seat
Outside Passenger Positions (Extended Cab)"
earlier in this section.
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